First, plain old microkernel? Show me a viable microkernel operating system that really functions like a microkernel OS should--with all device drivers in userspace and only the VM service in the kernel. Sure, MINIX, L4, Mach, Plan9, and others are headed down that path, but none have been successful. If Singularity really was a true microkernel operating system, that would be impressive.

As an aside: being a microkernel has never been a goal. And with managed code, it should be useless to be a microkernel, except if you would want all services restartable.